Question

A man of mass 60kg runs up a flight of 30 steps in 15 seconds. If each step is 20 cm high, calculate the power developed by the man.

Answer 1

each step = 20cm
30 steps = 30×20= 600 cm = 6 m
now, power = W/Time
for work to be done we need force × displacement
force= mg
therefore W= mgh
= 60 × 9.8 × 6
= 3528 J
power = W/T
= 3528 ÷ 15
= 235 watt. ans..

Answer 2

Given :

Mass (m) = 60 Kg

Height of each step = 20 cm

Number of steps taken = 30

Time taken to run up the flight (T) = 15 sec

To Find :

The power developed by the man.

Solution :

Force acting on the man = mass (m) × acceleration due to gravity (g)

                                          = 60 × 10

                                          = 600 N

Height of each step is 20 cm

So, Total distance covered = 20 × 30

                                             =  600 cm = 0.6 m

Power developed by the man =  $\frac{F . ds}{T}$

                                                  =  $\frac{600 * 0.6}{15}$

                                                  = 24 W

∴ The power developed by the man is 24 W.